Protective effects of crocodile muscle-derived peptide against D-galactose induced hippocampal aging and cognitive impairment in mice

Age-related cognitive decline is closely linked to hippocampal deterioration, in which oxidative stress plays a critical role. Crocodile meat peptide (CMP) is a naturally active peptide enzymatically isolated from crocodile skin and meat. It exhibits potential antioxidant and metabolic properties, and its neuroprotective role remains largely underexplored. This study investigated the protective effects of CMP against D-gal (D-galactose)-induced hippocampal aging and cognitive impairment in mice and elucidated the underlying mechanisms. CMP, prepared by enzymatic hydrolysis with alkaline protease and characterized by mass spectrometry (primary molecular weight < 2000 Da), was administered to a D-gal-induced aging mouse model. Behavioral tests showed that CMP supplementation significantly alleviated anxiety-like behavior in the open field test, improved recognition memory in the novel object recognition test, and enhanced spatial learning and memory in the Morris water maze. Histopathological analysis revealed that CMP attenuated D-gal-induced neuronal damage in the hippocampus, including disordered arrangement, reduced cell density, and loss of Nissl bodies. Concurrently, serum oxidative stress marker assays revealed that CMP significantly reduced serum Malondialdehyde levels in the model mice, corrected the abnormal compensation of Superoxide dismutase, and alleviated oxidative stress-induced damage. Mechanistically, CMP treatment significantly downregulated the mRNA expression of the senescence marker p21, modulated the autophagy adapter p62, and altered the expression of the anti-apoptotic protein BCL2 in the hippocampus. These findings indicate that CMP effectively ameliorates D-gal-induced cognitive deficits and hippocampal aging, likely by preserving neuronal integrity and modulating pathways involved in senescence, autophagy, and apoptosis. This study provides experimental evidence supporting CMP as a potential candidate for nutritional intervention in age-related cognitive decline for preventing or mitigating age-related cognitive decline.